Embodiments of the inventive concepts disclosed herein are directed generally to a system and related method for encrypting position data of an aircraft transmitted via the High Frequency Data Link (HFDL) protocol. HFDL uses the unique properties of high frequency (HF) radio waves (waves in the spectral band between 2.0 MHz and 30 MHz) to propagate long-range data or voice communications through the ionosphere (c. 30-375 miles above the earth's surface) at variable frequencies and transmission speeds (300, 600, 1200, or 1800 bps) depending on current propagation conditions (e.g., atmospheric temperature or electron density). The HFDL infrastructure incorporates a network of dedicated HF ground stations (HGS), currently comprising 15 HGS worldwide, each having an effective radius around 3,000 NM and thereby providing overlapping coverage over six continents. The network of HGS allows for single-hop and multi-hop transmissions over great distances and through transoceanic airspace underserved, or unserved, by surveillance radar or automatic dependent surveillance-broadcast (ADS-B) services.
Aircraft tracking sites such as FlightAware (flightaware.com) or other aircraft situation display to industry (ASDI) vendors allow the general public to track the position, heading, destination, tail number, or other particular details of commercial and civilian flights in near-real time, based on data from traffic control radar, ADS-B transmissions to and from the aircraft, or aircraft data link services using HFDL or similar protocols (e.g., Aircraft Communications Addressing and Reporting System (ACARS) or satellite communications (SATCOM)). For example, a hobby-grade shareware program called PC-HFDL allows any end user with a home computer to decode HFDL data traffic. While FlightAware cannot decode HFDL, PlanePlotter (www.coaa.co.uk/planeplotter.htm) employs PC-HFDL to provide a graphic display of tracked aircraft similar to that provided by FlightAware, but including those aircraft reporting their position via HFDL.
Aviation customers may have valid business reasons for preventing the general public (in particular, their competitors) from tracking the positions or flight plans of their aircraft and making inferences therefrom. Currently, only two options are available to those wishing to block public tracking of their aircraft, both of which are associated with particular drawbacks. A request may be filed with the FAA to block entirely a given aircraft tail number (thereby preventing any tracking data for that tail number from being broadcast to ASDI vendors). Similarly, a customer may request selective blocking of a given tail number from an ASDI vendor (in which case tracking data is still broadcast to the vendor, but the vendor agrees not to display it). In the first case, an FAA source block prevents a party (or, e.g., interested friendly personnel such as administrative staff or family members) from tracking its own aircraft. In the second case, a party may be required to contact multiple vendors to achieve selective blocking; in addition, charges may be associated with this service.